1. Field of the Invention
The present invention relates to an oscillator whose frequency is controllable by a current variation and it is intended that such an oscillator replace the presently-employed voltage-controlled oscillators.
2. Description of the Prior Art
Numerous voltage-controlled oscillators (VCO) are known in the art. In most of such oscillators, the oscillator frequency is altered via capacitance diodes. From the German Letters Pat. No. 2,803,400 an oscillator circuit is known which, via a current distributor circuit, connects an additional capacitance to the resonant circuit capacitance. Also in this circuit, a reactance is varied.
In the article "Integrated Circuit Phase-Locked Loops", by R. R. Cordell, from the Conf. Record, 1976, Intern. Conf. on Communications, 12th IEEE Intern. Conf., Philadelphia, June 14-16, 1976, pp. 10-12 to 10-16 TIB-RN 272 (12), current-controlled oscillators (CCO) are described on Pages 10-13 to 10-15.
In FIG. 6 of the above article, a multivibrator whose frequency is controlled by emitter currents is disclosed. A frequency-determining capacitance is reversed at varying speed. However, this circuit exhibits disadvantages which are known per se in the case of multivibrators, such as an unclean frequency spectrum and poor frequency stability. Moreover, an applicable oscillator circuit requires a considerable circuit expense.